introduction and review of literatureshodhganga.inflibnet.ac.in/bitstream/10603/5288/9/09_chapter...
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INTRODUCTION AND
REVIEW OF LITERATURE
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MODIFIED ATMOSPHERE PACKAGING OF READY TO COOK
IDLI BATTER
1.1 INTRODUCTION
Fermented cereals, pulses and meat are consumed throughout the world both as means of
preservation by identifying their texture, aroma and flavour in addition to their health
benefits. Idli, one of the most common traditional cereal-pulse based fermented breakfast
product is consumed mostly in the southern part of India and Sri Lanka. Idli is the most
preferred breakfast product due to its soft texture, mild pleasant flavour and aroma, easy
digestibility and known health and nutritional benefits. Even with rapid social transition,
idli still remains to be the choice of breakfast for the population either at home or home-
away. With rapid urbanization, idli is one of the most served products in the restaurants
and catering establishments. Idli being a lactic acid bacteria fermented product, is
traditionally prepared by rice and dhal soaked, ground and fermented before steamed and
consumed. With rapid urbanization, Ready to cook, packaged fermented batter is made
available in the cities by household vendors, frequently with quality and safety problems.
In spite of heavy demand there has not been proper commercialization of the product due
to lack of set quality parameters as well as issues with the shelf life of the product. There
has also been an effort made to develop starter cultures aimed at preparing the final
product with consistent sensory parameters. However these starter cultures did not
become popular due to their inferior sensory characteristics. Efforts are being made by
various research groups to develop appropriate and acceptable starter cultures for idli.
In spite of heavy demands organized food industries have not taken up the
commercialization of ready to cook idli batter in view of short shelf life. Even the
commercial prospects of scientifically developed starter cultures will remain curtailed till
the shelf life of ready to cook batter is considerably extended.
In the pursuit of extension of shelf life of ready to cook idli batter, a microbiologically
dynamic fermentation medium with other several factors needs to be kept in mind. The
product should be close to the natural as any change in the dynamics of the fermentation
flora could lead to unacceptable product characteristics. Although only a few fermented
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products or preserved with Modified Atmosphere Packaging (MAP), most of them are
packaged after the fermentation/maturation process.
In this work an effort has been made to scientifically optimize the process of preparation
of ready to cook idli batter and packaging the ground product in the initial stages of
fermentation with optimized gas combinations supporting slow but desirable
fermentation process extending the product shelf life without affecting texture and
sensory characteristics.
1.2 REVIEW OF LITERATURE
The review of literature of the current study is done under the following headings:
1.2.1. Significance of fermented foods
1.2.2. Positive health outcomes of breakfast consumption
1.2.3. Idli and its properties
1.2.4. Rice - A staple food grain in idli making
1.2.5. Black gram - A protein source in idli making
1.2.6. Oligosaccharides in foods
1.2.6. Shelf life of fermented foods
1.2.1. SIGNIFICANCE OF FERMENTED FOODS
Fermented foods are those foods which have been subjected to the action of
microorganisms or their enzymes to produce desirable biochemical changes and results in
significant modification to the food. Fermented foods provide variety to the diet
supplying nutrients predominantly proteins and amino acids. The process of fermentation
also aids in detoxification (Campbell-Platt, 1994). Fermentation plays diverse roles like
enhancing the diet with wide range of flavours, aromas and textures, preserving
substantial amounts of food through lactic acid, alcoholic, acetic acid, alkaline
fermentations, enriching food substrates with nutrients and also reducing cooking times
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and fuel requirements (Steinkraus, 1994). Lactic acid fermented foods are common in
tropical countries and these foods give improved organoleptic qualities (Cookey et al.,
1987).
Fermentation affords a natural way to reduce the volume of the material to be
transported, abolish undesirable components, enhance the nutritive value and improve
appearance of the food, decrease the energy required for cooking and make a safer
product (Simango, 1997). Fermented foods are produced worldwide by various
manufacturing techniques, raw materials and microorganisms. However, there are only
four main fermentation processes which include alcoholic, lactic acid, acetic acid and
alkali fermentation (Soni and Sandhu, 1989). Alcohol fermentation results in the
production of ethanol, and yeasts are the predominant organisms (e.g. wines and beer),
fermented milks and cereals are mainly conceded out by lactic acid bacteria. A second
group of bacteria significant in food fermentation is the acetic acid producers
(Acetobacter species). Acetobacter sp. converts alcohol to acetic acid in the presence of
excess oxygen (McKay and Baldwin, 1990). Likewise, fermentation significantly
improves the protein quality as well as the level of amino acid particularly lysine in
maize, millet, sorghum, and other cereals (Hamad and Fields, 1979). Fermentation also
leads to improvement in the shelf life, texture, taste and aroma of the final product.
During cereal fermentation a number of volatile compounds are formed, which contribute
to a composite blend of flavours in the products (Chavan and Kadam, 1989).
The presence of aromas representative of acetic acid and butyric acid make fermented
cereal based products more appetizing. Traditional fermented foods prepared from most
common types of cereals (such as rice, wheat, corn or sorghum) are well known in
various parts of the world. Some are utilized as colorants, spices, beverages and breakfast
or light meal foods, while a few of them are used as key foods in the diet. The
microbiology of many of these fermented products is quite complex and not known. In
most of these products, fermentation is natural and involves mixed cultures of yeasts,
bacteria and fungi. Some microorganisms may participate in parallel, while others act in a
sequential manner with exchanging dominant flora during the course of the fermentation.
The common bacteria involved in fermentation are species of Leuconostoc,
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Lactobacillus, Streptococcus, Pediococcus, Micrococcus and Bacillus. The fungi genera
Aspergillus, Paecilomyces, Cladosporium, Fusarium and Saccharomyces (yeast) are most
often found in certain products (Blandino et al, 2003).
1.2.2. POSITIVE HEALTH OUTCOMES OF BREAKFAST CONSUMPTION
Studies done by Agostoni, et al., (2010) disclose that breakfast represents a healthy habit
and association with positive health outcomes proves breakfast should be consistent with
local and family dietary behaviours. Policies and interventions supportive of breakfast
consumption are therefore encouraged. According to neurobehavioral data, the good
example of parents and access to a variety of palatable and pleasant breakfast foods
should drive children to choose self select breakfast models with balanced composition,
while respecting recommended dietary allowances. A balanced macronutrient
composition, the proposition of a variety of models leading to a total energy density
preferably within lower ranges (< 1 to 1.5), as well as glycemic indices in the lower range
for the same food class, could emphasize the positive short and long term health
outcomes which is now attributable to breakfast.
Regular breakfast consumption can have a multitude of positive health benefits, yet
young people are more likely to skip breakfast than any other meal. Given the evidence
that dietary behaviours established in childhood and adolescence track into adulthood
along with evidence that breakfast skipping increases with age, identifying correlates of
children's and adolescent's breakfast behaviour is imperative. Few studies have examined
the same specific family correlates of breakfast consumption, limiting the possibilities of
drawing strong or consistent conclusions. Parental breakfast eating and living in two-
parent families were the correlates supported by the greatest amount of evidence in
association with adolescent's breakfast consumption. The results suggest that parents
should be encouraged to be positive role models to their children by targeting their own
dietary behaviours and that family structure should be considered when designing
programmers to promote healthy breakfast behaviours (Pearson et al., 2009).
Eating breakfast is important for the health and development of children and adolescents.
Reports on the findings of an Australian survey of 699 thirteen year old concerning the
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extent of skipping breakfasts, indicated approximately 12 percent of the sample skipped
breakfast. Gender was the only statistically significant socio demographic variable, with
females skipping at over three times the rate of males. Skippers were more likely to be
dissatisfied with their body shape and to have been on a diet to lose weight than were
those who ate breakfast (Shaw, 1998).
Wesnes et al., (2003) reported in their study that a typical breakfast of cereal rich in
complex carbohydrates can help maintain mental performance over the morning.
Frequency of breakfast and cereal consumption decreased with age. Days eating breakfast
were associated with higher calcium and fiber intake in all models, regardless of
adjustment variable. After adjusting for energy intake, cereal consumption was related to
increased intake of fiber, calcium, iron, folic acid, vitamin C, zinc, and decreased intake
of fat and cholesterol. Cereal consumption as part of an overall healthful lifestyle may
play a role in maintaining a healthful Body Mass Index (BMI) and adequate nutrient
intake among adolescent girls (Barton et al., 2005).
1.2.3. IDLI AND ITS PROPERTIES
1.2.3.1. Nutritional composition of idli
Idli, a very popular fermented breakfast food consumed in the Indian subcontinent,
consists mainly of rice and black gram. Idli fermentation was carried out in the
conventional way in a batter having rice to black gram in the ratios of 2:1, 3:1 and 4:1 at
room temperature. It makes an important contribution to the diet as a source of protein,
calories and vitamins, especially B-complex vitamins, compared to the raw unfermented
ingredients. It can be produced locally and used as a dietary supplement in developing
countries to treat people suffering from protein calorie malnutrition and kwashiorkor
(Nagaraju and Manohar, 2000).
Adding Saccharomyces cerevisiae, along with natural bacterial flora of the ingredients,
was the best method for standardizing idli fermentation in terms of improved
organoleptic characteristics, leavening and nutritional constituents. Traditional idli
fermentation involves several bacteria and yeasts, contributed by the ingredients rice
(Oryza sativa), black gram (Phaseolus mungo) and the environment, with overall
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dominance of the former in bringing about various changes. Idli fermentation is
accompanied by an increase in total acids, batter volume, soluble solids, reducing sugars,
non protein nitrogen, free amino acids, amylases, proteinases and water soluble vitamins
B1, B2 and B12 contents, thus accounting for improved digestibility and nutritional value
of the staples. Novel idli batter prepared by replacing conventional black gram with other
legumes, revealed significant change but with difference in the levels of some
biochemical constituents (Soni and Sandhu, 1989).
Idli, Dhokla, Nan, Kulcha, Bread, Jalebi, Bhatura, Bhalla, Dosa, Gulgule and Wadian
were prepared in the laboratory using traditional fermentation techniques. The fermented
batter of idli and dosa contained higher amount of available lysine, cystine and
methionine. After processing, maximum retention of lysine, methionine and cystine was
observed in steamed idli (Riat and Sadana, 2009).
Growth and nitrogen balance feeding trials were conducted with rats to determine the
protein quality of idli, a fermented steamed cake prepared from beans (Phaseolus
vulgaris) and rice. Feed Efficiency Ratio (FER), Protein Efficiency Ratio (PER) and
Relative PER (RPER) of fermented idli diets were significantly lower (p<0.05) than the
FER, PER and PER of unfermented idli diets. The Digestibility Coefficient (DC) and Net
Protein Utilization (NPU) of fermented idli diets were significantly lower (p<0.05) than
the DC and NPU of unfermented idli diets. Biological Value (BV) of fermented and
unfermented idli diets was similar to the BV of a caesin control diet. Fermentation does
not improve the protein quality of idli prepared from beans and rice (Joseph and
Swanson, 1994).
1.2.3.2. Physico chemical parameters of idli
Balasubramanian and Viswanathan (2007a) has shown that idli batter was prepared from
soaking polished parboiled rice and decorticated black gram. The blend a ratio of 2:1, 3:1
and 4:1 (v/v) and the batter was allowed for fermentation (0, 6, 12, 18 and 24 h) adding
two percent of salt. Other legumes such as soybeans and Great Northern beans could be
substituted for black gram in preparation of idli (Reddy et al., 1981). Fermentation time
of the batter varies from 14 to 24 h with overnight fermentation being the most frequent
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time interval. The ingredients for idli are carefully washed, soaked in water separately,
grounded, mixed, and finally allowed to ferment overnight. When the batter has been
raised sufficiently, it is cooked by steaming and served hot. The product has a very soft
and spongy texture and a desirably sour flavour and taste. The black gram was washed
several times, first with tap water and finally with distilled water to remove the surface
microorganisms. These were found to produce off flavour in the idli unless they were
washed out (Mukherjee et al., 1965).
Mukherjee et al., (1965), studied the fermentation of idli batter. The microorganisms
responsible for the characteristic changes in the batter were isolated and identified.
Although there is a sequential change in the bacterial flora, the predominant
microorganism responsible for souring, as well as for gas production, was found to be
Leuconostoc mesenteroides. In the later stages of fermentation, growth of Streptococcus
faecalis and, followed by Pediococcus cerevisiae became significant. The fermentation of
idli demonstrates a leavening action caused by the activity of the hetero fermentative
lactic acid bacterium, L. mesenteroides. As far as is known, this is the first record of a
leavening action produced exclusively by the activity of a lactic acid bacterium.
Idli is traditional fermented rice and black gram based breakfast food of South India. Idli
batter was prepared from soaking polished parboiled rice and decorticated black gram for
4 h at 30 ± 1oC in water. The soaked mass was ground to 0.5 to 0.7 mm particle size
batter using wet grinder with adequate amount of water. The idli batter parameters such
as bulk density, pH, total acidity, flow behaviour index and consistency coefficients were
studied for different fermentation times and blend ratios. The bulk density, pH and
percentage total acidity of batter during different fermentation times and blend ratios
ranged between 0.94 and 0.59 g/cm3, 5.9 and 4.1 and 0.443 and 0.910%, respectively.
The consistency coefficient at any fermentation time shows increasing trend as the rice to
black gram ratio increased. The flow behaviour index indicated strong non-Newtonian
fluid behaviour (pseudoplastic) of idli batter at different fermentation times and blend
ratios (Balasubramanian and Viswanathan 2007a).
The rheology of the idli batter was assessed using a Brookfield viscometer having disc
spindles. Power law model with yield stress adequately fitted the data. Yield stress values
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were in the range of 13-43 Pa and reached a maximum value at 7 h of fermentation. Flow
behaviour indices were in the range of 0.287-0.605. Flow behaviour indices at 23 h were
significantly lower than those at 0 h. Consistency index values, at any fermentation time,
increased as the rice to black gram ratio increased. Mean particle size ranged from 500 to
600 micro meter and there was no definite trend noticed with respect to time of
fermentation and rice to black gram ratio. There was a steep change in volume increase
after 4-h fermentation (Nagaraju and Manohar, 2000).
The idli batter comprises lactic acid bacteria and yeasts and causes an improvement in the
nutritional, textural and flavour characteristics of the final product. The desirable flavour
compounds such as ketones, diols and acids were found to be present up to eight days of
storage, whereas undesirable flavours like sulphurous and oxazolidone compounds,
ethanone and thiazole appeared in the batter subsequent to six days of storage. The
sensory attributes of idli (final product) prepared from the stored batter related well to the
determined flavour profile (Agrawal et al., 2000).
The work done by Nisha et al., (2005) stabilized the idli batter at room temperature (28-
30°C) and refrigerated storage (4-8°C) by using various hydrocolloids and some surface-
active agents. The batter was evaluated in terms of decrease in volume, and whey
separation. While hydrocolloids gave good stabilization, surface-active agents failed to
stabilize the batter and they reduced whey separation. Among the various hydrocolloids,
0.1percent guar gave best batter stabilization, and idli made after ten days of room
temperature and 30 days of refrigerated storage of batter were found to be of acceptable
quality.
Reduction in the fermentation time of the idli batter is of great commercial significance
for large-scale idli production and can be potentially achieved by addition of enzymes.
The study done by Iyer and Anathanarayan, (2008) was undertaken to explore the
possibility of expediting the idli batter fermentation process by adding an exogenous
source of α-amylase enzyme. 5, 15 and 25 U per 100 g batter of amylase added to the idli
batter was allowed to ferment. Different parameters were monitored and sensory
attributes were also studied and compared with that of the control set. The fermentation
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time was reduced from a conventional 14 h to 8 h and the sensory attributes of the final
product were also successfully maintained.
Texture Profile Analysis (TPA) test was performed for idli, making cylinder samples
(13.5 mm diameter, 10 mm long) of idli. In Pearson correlation matrix, majority of the
parameters were positively correlated at p<0.01 and p<0.05. The firmness value
positively correlated with gumminess and chewiness, which depicts the soft nature of idli
(Balasubramanian and Viswanathan 2007b).
1.2.4. RICE - A STAPLE FOOD GRAIN IN IDLI MAKING
Cereal grains particularly rice, form a major source of dietary nutrients for all people,
particularly those in the developing countries. However, compared with animal foods,
nutritional quality of cereal grains is inferior due to lower protein content, deficiency of
certain essential amino acids, lower protein and starch availabilities, and the presence of
some antinutritional factors. Fermentation of cereals for a limited period of time
improves amino acid composition and vitamin content, increases protein and starch
availabilities, and lowers the levels of antinutrients. The traditional foods prepared by
fermentation of cereals in different parts of the world are briefly described and future
research needs to improve their nutritional contribution are addressed (Chavan et al.,
1989).
Cereals are deficient in lysine, but are rich in cysteine and methionine. Legumes, on the
other hand, are rich in lysine but deficient in sulphur containing amino acids. Thus, by
combining cereal with legumes, the overall protein quality is improved (Camphell-Platt,
1994). Fermented foods prepared from cereals and legumes are an important part of the
human diet in Southeast Asia and parts of East Africa. The popularity of legume based
fermented foods is due to desirable changes including texture and organoleptic
characteristics. Improvement in digestibility and enhancement of keeping quality, partial
or complete elimination of anti-nutritional factors or natural toxins, increased nutritive
value, and reduced cooking time (Joseph, 1994).
Cereal grains constitute a major source of dietary nutrients all over the world. Although
cereals are deficient in some basic components, fermentation may be the most simple and
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economical way of improving their nutritional value, sensory properties, and functional
qualities. Products produced from different cereal substrates (sometimes mixed with
other pulses) fermented by lactic acid bacteria, yeast and/or fungi (Blandino et al., 2003).
Rice colour changes from white to amber during parboiling (soaking and steaming).
Colour parameters indicated that, during soaking, yellow bran pigments leaches out in the
water. The levels of the Maillard precursors (i.e., reducing sugars and free α-amino
nitrogen (FAN)) depends on soaking temperature and time: leaching of RS was
compensated by enzymatic formation for long soaking times (>60 min), while proteolytic
activity was too low to compensate for FAN leaching. Parboiled rice soaking under
nitrogen, oxygen, or ambient conditions and determination of polyphenol oxidase activity
allowed to conclude that the effect of enzymatic colour changes on the soaked rice colour
was rather small. Colour measurements of brown and milled mildly, intermediately, and
severely parboiled rice samples showed that both brown and milled rice samples were
darker and more red and yellow after parboiling and that the effect depended on the
severity of parboiling conditions. Furthermore, steaming affected the rice colour more
and in a way opposite to that observed in soaking (Lamberts et al., 2006).
Parboiled brown rice contained considerably more Reducing Sugars (RS) but less sucrose
and Free Amino Acids (FAA) than raw brown rice. On milling, there was considerable
loss of sucrose and FAA from raw rice, but very little from parboiled rice; reducing
sugars changed little in either. Processing conditions affected the contents of sugars and
FAA. Maximum increase in RS and decrease in sucrose content occurred after soaking at
60C. Controlled incubation of rice flour, intact grain, separated germ and deemed rice in
water showed that considerable changes in sugars and FAA occurred in all cases, the
magnitude depending on the circumstances, but a greater part of the sugars leached out
into the water during soaking (Ali and Bhattacharya, 1980).
Grinding characteristics of raw and parboiled rice were evaluated in various wet grinding
systems like, mixer grinder, stone grinder and colloid mill. The duration of grinding had
inverse effect on the particle size and direct impact on the starch damage as well as
energy consumption in batch grinders. Stone grinder was the least energy efficient and
specific energy consumption for grinding raw rice (160.6 kJ/kg) was nearly twice as that
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of mixer grinder (74.9 kJ/kg). Parboiled rice required longer duration of grinding
compared to raw rice, consequently specific energy consumption was higher (∼220
kJ/kg) (Sharma et al., 2008). Wet grinding is a critical step in the preparation of batter
based traditional food products. It involves both physical and chemical changes while dry
grinding is a mere size reduction operation. In wet grinding of cereals, the protein matrix
holding the starch granules is destroyed, releasing the starch granules from the protein
network (Kent and Evers, 1994). A colloid mil was comparatively evaluated with
domestic wet grinding systems, namely, a mixer grinder and a stone grinder for grinding
of raw rice, parboiled rice and black gram. The wet ground samples were finer in particle
size compared with dry ground samples. The starch damage was the least in black gram
followed by raw rice and parboiled rice in dry grinding. In wet grinding, the starch
damage in black gram as well as raw rice remained more or less same whereas the
parboiled rice showed greater damage. Parboiled rice required 2.5 to 3 times more energy
(216-252 kJ/kg) as that of raw rice (72-108 kJ/kg) for grinding in the mixer grinder and
the stone grinder (Solanki et al., 2005)
The nutritional quality of wild rice tends to be comparable with other cereals
characterized by a high content of starch and protein and a low fat content. As a whole
grain, wild rice is also a good source of dietary fibre (Qiu et al., 2010).The presence of
Streptococcus faecalis in the fermented batter, the presence of pharmacological active
amines such as thiamine was expected but they were not detected (VanVeen, et al.,
2008).
Parboiled brown rice contained considerably more (RS) but less sucrose and FAA than
raw brown rice. On milling, there was considerably loss of sucrose and FAA from raw
rice, but very little from parboiled rice; reducing sugars and FAA. Maximum increase in
RS and decrease in sucrose content occurred after soaking at 600
C (Ali et al., 2007).
Larsen et al., (2000) opines that rice is an important crop, forming a staple food for many
of the world‘s population. A study showed there was an effect of severely pressure
parboiled rice reduced the glycaemic index.
Brown rice malt from Indica and Japonica type rice were prepared and their nutrient
composition as well as Non-Starch Polysaccharide (NSP) contents and also some of the
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physicochemical characteristics were determined. The activity of α- and β-amylases in
the un-germinated (native) rice was negligible but increased considerably on germination.
Malting altered the chemical composition of both Indica and Japonica rice to a small
extent but caused noticeable changes in the pasting characteristics. Controlled
germination or malting causes considerable changes in the physicochemical and
biochemical properties of both Indica and Japonica rice (Mohan et al., 2010). Whole
grain rice is rich in phenolic compounds. The effect of γ-irradiation on the main phenolic
compounds in the rice grains of three genotypes (black, red, and white) was investigated.
Three phenolic acids (p-coumaric acid, ferulic acid, and sinapinic acid) were identified as
major phenolic compounds in all rice samples, while two anthocyanins (cyanidin-3-
glucoside and peonidin-3-glucoside) were identified in pigmented grain samples (Zhu et
al., 2010).
1.2.5. BLACK GRAM A PROTEIN SOURCE IN IDLI MAKING
Blackgram (Phaseolus mungo) is a pulse traditionally used in the preparation of
South Indian breakfast foods, such as idli, which is relished for its soft and spongy
texture (Susheelamma and Rao, 1979a). The components responsible for these
properties are the surface active proteins that generate a foam and as a result
impart a porous structure to the food, and the viscogenic mucilaginous
polysaccharide (~6%) that stabilizes the porous structure against thermal disruption
during steaming. The overall carbohydrate composition (Bhat and Tharanathan,
1986) and the structure function characteristics of the total polysaccharides of black
gram have been reported. During fermentation of black gram, for the preparation of
leavened foods, it was found that the mucilaginous polysaccharide undergoes
compositional and rheological changes (Muralikrishna et al.,1987). Here, the
fermentation is due to the activities of endogenous microflora (endophytes) in black
gram, in particular Leuconostoc mesenteroides, yeasts, lactic acid bacteria and
coliforms. More than one oligosaccharide was observed as in green gram (stachyose,
maltohexaose), sorghum (stachyose, maltotriose), barley (stachyose, raffinose), wheat
(stachyose, raffinose) and black gram (stachyose, raffinose). In ragi, bajra and rice malt
oligosaccharides were absent. Germination of seeds for 48 h resulted in complete loss of
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stachyose and raffinose in cereals and pulses. The maltotriose content in pulses
completely disappeared on germination but among cereals, 45.1 and 57.3 percent loss
was observed in sorghum and maize, respectively (Sampath et al., 2008). In black gram
after fermentation, apparent viscosity of cold paste increased. Some of the properties such
as intrinsic viscosity, swelling and solubility after fermentation were reported by them.
Fermentation and steaming approximately 40 per cent reduction in oligosaccharides
resulting in reduced flatulence in the body (Koh and Singh, 2009).
Nutritional benefits are produced in legume fermentations, when microorganisms break
down the flatulence causing indigestible oligosaccharides, such as stachyose and
verbascose are broken down into the absorbable monosaccharaides and disaccharides.
Biosynthesis of B vitamins in food fermentations has been recognized to be of major
nutritional significance, particularly in Africa where high-carbohydrate diets, particularly
maize diets can be deficient in essential B vitamins, the significance of B vitamin
synthesis during fermentation to maize and sorghum beers in southern Africa was
recognized by the use of the term ‗biological ennoblement‘ by Platt (1964).
1.2.6. OLIGOSACCHARIDES IN FOODS
Carbohydrates are classified into monosaccharide, disaccharides, oligosaccharides and
polysaccharides. Oligosaccharides are low molecular weight carbohydrates consisting 3
to 10 sugar monomers (Voragen, 1998). Oligosaccharides withstand salivary hydrolysis
and digestive enzymes of human animal intestine so these oligosaccharides are not
absorbed in the upper digestive tract and are able to reach the colon unaltered. In colon,
oligosaccharides interact with the microflora and affecting immunomodulation (Reiffova
and Nemcova, 2006). The non-digestible oligosaccharides promote the growth of
beneficial bacteria in the colon, chiefly the Bifidobacteria sp., and are thus recognized as
prebiotics (Mussatto and Mancilha, 2006). Most of the known prebiotics and prebiotic
candidates are nondigestible oligosaccharides, obtained by extraction from plants (e.g.,
chicory inulin), followed by enzymatic hydrolysis (e.g., oligofructose from inulin) and by
synthesis (by trans-glycosylation reactions) from mono and/or disaccharides such as
sucrose (fructooligosaccharides) and lactose (trans-galactosylated
oligosaccharides/galactooligosaccharides) (Crittenden and Playne, 1996). Among the
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prebiotics, inulin and oligosaccharides are the most studied and have been recognized as
dietary fibre worldwide (Moshfegh et al., 1999).
1.2.6.1Conversion of polysaccharides into oligosaccharides
Polysaccharides are the major source of bioactive oligosaccharides and around twenty
different types of non-digestible oligosaccharides (NDOs) are described for prebiotic
activities. Fructooligosaccharides, galacto-oligosaccharides, xylo-oligosaccharides and
galacturono-oligosaccharides are predominant NDOs with prebiotic characteristics.
Oligosaccharides are recognized as non-cariogenic, non-digestible and low-calorie
molecules and can be used as natural food preservatives. Chitosan and oligochitosans,
inhibits growth of pathogens and extends shelf-life of food products (Barreteau et al.,
2006).
Glycosyl-hydrolases and polysaccharide lyases, are used to obtain oligosaccharide from
polysaccharides. Polysaccharide chains were broken down by polysaccharide lyases and
form a double bond at new reducing end (Michaud et al., 2003). Polysaccharide
hydrolase cleave glycosidic bond by transfer of a H2O molecule and act as
exohydrolases/endohydrolases (Boels et al., 2001; Bojarova and Kren, 2007). Enzyme
used for the purpose must be specific to the substrate should be more efficient. The
solution for having enzyme specificity is to use bacteria to produce particular enzyme.
From the bacteria the specific enzyme of the polysaccharide can be isolated, purified and
concentrated and used (Sutherland, 1999).
1.2.6.2. Physiological properties of oligosaccharides
Oligosaccharides possess important physicochemical properties. They are used as food
ingredients as their physiological properties were beneficial to human health. The NDOs
can be used as low caricinogenic sugar surrogates in products like confectionery,
chewing gums, yoghurts and drinks (Crittenden and Playne, 1996). Many NDOs are not
digested by humans because the human body doesn‘t have the enzymes necessary to
hydrolyze certain units of monosaccharides. Compounds include carbohydrates where
fructose, galactose, glucose and/or xylose are the monosaccharides units. This property of
NDOs makes the suitable for use in sweet, low-caloric diet foods, and for consumption
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by individuals with diabetes (Crittenden and Playne, 1996; Rivero-Urgell and
Santamaria-Orleans, 2001).
Most oligosaccharides were quantitatively hydrolyzed in the upper part of the GIT. The
resulting monosaccharides are transported through the portal blood to the liver and
subsequently, to the circulatory system. These carbohydrates are important for health as
they serve as both substrates and regulators for major metabolic pathways. Nevertheless,
some oligosaccharides present specific physicochemical properties resist to the digestive
process, reaching the caeco colon. In the caeco-colon, most of the nondigestible
oligosaccharides were hydrolyzed to small oligomers and monomers and further
metabolized by most of the anaerobic bacteria. Such a metabolic process, known as
fermentation, not only serves the bacteria by providing energy for proliferation, but it
also produces gases (H2, CO2, CH4), which are metabolically useless to the host, and
small organic acids (Short-Chain Fatty Acids – SCFA) such as acetate, propionate,
butyrate and L-lactate. Even though they do not provide the body with monosaccharaides,
the non-digestible oligosaccharides are indirect energy substrates and metabolic
regulators (Delzenne and Roberfroid, 1994). The amounts and types of SCFA produced
in the colon depend on the type of NDO substrate as well as on the composition of the
intestinal flora (Sako et al., 1999).
Oligosaccharides serve as substrate for growth and proliferation of anaerobic bacteria,
mainly the Bifidobacteria, which inhibit the growth of putrefactive and pathogenic
bacteria present in the caeco-colon (Sangeetha et al., 2005).
NDOs leads to decrease of pH in the colon and consequently, in faeces, resulting from
the production of SCFA. Lower pH values inhibit the growth of certain pathogenic
bacteria species while stimulating the growth of the bifidobacteria and other lactic acid
species (Manning and Gibson, 2004). An increase in faecal dry weight excretion, which
is related to the increased number of bacteria resulting from the extensive fermentation of
NDOs (Bielecka et al., 2002)
The indigestible quality of NDOs means that they have effects similar to dietary fibre,
and thus prevent constipation. The end products of NDOs fermentation by colonic
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bacteria, the SCFA, are efficiently absorbed and utilized by the human colonic epithelial
cells, stimulating their growth as well as the salt and water absorption, increasing thus the
humidity of the fecal bolus through osmotic pressure, and consequently improving the
intestinal motility (Rivero-Urgell and Santamaria-Orleans , 2001). NDOs help in
inhibition of diarrhea, especially when it is associated with intestinal infections
(Roberfroid and Slavin, 2000).
An increase in absorption of different minerals, such as iron, calcium, and magnesium
take place due to the binding/sequestering capacity of the NDOs. The minerals that are
bound/sequestered and, consequently, are not absorbed in the small intestine reach the
colon, where they are released from the carbohydrate matrix and absorbed. The increase
on calcium absorption, in particular, reduces the risk of osteoporosis since this mineral
promotes an increase in the bone density and bone mass. The hypotheses most frequently
proposed to explain this enhancing effect of NDOs on mineral absorption are the osmotic
effect, acidification of the colonic content due to fermentation and production of SCFA,
formation of calcium and magnesium salts of these acids, hypertrophy of the colon wall
(Younes, 1996).
Beneficial effect on the carbohydrates and lipids metabolism is that oligosaccharides lead
to a decrease in the cholesterol, triglycerides and phospholipids concentration in the
blood, reducing thus the risk of diabetes and obesity. Changes in the concentration of
serum cholesterol have been related with changes in the intestinal microflora. Some
strains of Lactobacillus acidophilus assimilate the cholesterol present in the medium,
while others appear to inhibit the absorption of cholesterol through the intestinal wall. On
the other hand, the changes in lipid metabolism were suggested to be a consequence of a
metabolic adaptation of the liver that might be induced by SCFA (Daubiol et al., 2000).
NDOs aid in reduction of cancer risk, mainly the gut cancer. This anti-carcinogenic effect
appears to be related to an increase in cellular immunity, the components of the cell wall
and the extra-cellular components of bifidobacteria. Faecal physiological parameters such
as pH, ammonia, p-cresol, and indole are considered to be risk factors not only for colon
cancer development but also for systemic disorders. It has been demonstrated in a human
study that the intake of trans-galactosylated disaccharides reduces the faecal pH as well
17
as ammonia, p-cresol and indole concentrations with an increase in bifidobacteria and
lactobacilli and a decrease in bacteroid populations. These alterations may be considered
to be beneficial in reducing the risk of cancer development. A low colonic pH may also
aid in the excretion of carcinogens (Delzenne and Roberfroid ,1994)
1.2.6.3 Animal studies on Oligosaccharides
Feeding mice with diets supplemented with inulin and oligofructose increased activities
of natural killer cells and phagocytes and enhanced T-lymphocyte functions compared to
mice fed diets with cellulose or lacking fibre. These results are consistent with the
observations of heightened resistance to systemic infections with Listeria spp. and
Salmonella spp., the lower incidence and growth of tumours after exposure to
carcinogens and transplanted tumour cells and are in agreement with enhanced innate and
acquired immune functions provided by Lactobacillus and other LAB. Supplementing
diets with FOS should increase production of SCFA, and particularly butyrate, and can be
predicted to strengthen mucosal defences and enhance response to health challenges
(Buddington et al., 2002).
Colonic fermentation of FOS results in the synthesis of short chain fatty acids, which
influences the lipid metabolism in human beings. Feeding male Wistar rats on a
carbohydrate rich diet containing 10 percent FOS significantly lowers serum
triacylglycerol (TAG) and phospholipid concentration (Delzenne et al., 2002).
FOS reduces post-prandial triglyceridemia by 50% and avoids the increase in serum free
cholesterol level occurring in rats fed with a Western type high fat diet. FOS protects rats
against steatosis (liver TAG accumulation) induced by fructose, or occurring in obese
Zucker fa/fa rats. FOS given at the dose of 10 percent in the diet of male Wistar rats for
30 days reduces postprandial insulinemia by 26 percent (Daubiol et al., 2000).
Animal studies provide strong evidence that FOS inhibit secretion of TAG rich Very Low
Density Lipoprotein (VLDL) particles via inhibition of de novo fatty acid synthesis. High
levels of fat present inmost human diets mean that rates of hepatic de novo fatty acid
synthesis are extremely low, since exogenous dietary fatty acids provide all the required
substrate for hepatic triacylglycerol synthesis (Parks, 2002).
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Dietary treatment with inulin/oligofructose (15 percent) incorporated in the basal diets for
experimental animals resulted in (a) reduction of the incidence of mammary tumours
induced in Sprague Dawley rats by methyl-nitrosourea (b) inhibited the growth of
transplantable malignant tumours in mice and (c) decreased the incidence of lung
metastases of a malignant tumour implanted intramuscularly in mice. It is reported that
the dietary treatment with FOS/inulin significantly potentiated the effects of sub-
therapeutic doses of six different cytotoxic drugs commonly utilized in human cancer
treatment (Taper and Roberfroid, 2002).
Roberfroid and Slavin, (2000) has reported that feeding rats with FOS (10 percent) for a
few weeks decreased uremia in both normal and nephrectomized rats. Dietary FOS
enhanced faecal nitrogen excretion and reduced renal excretion of nitrogen in rats. This
occurs because these fermentable carbohydrates serve as energy source for the intestinal
bacteria, which during growth also require a source of nitrogen for protein synthesis.
1.2.6.4 Applications of FOS in food formulations
Inulin and oligofructose are ingredients that deliver a number of important nutritional
benefits as well as contribute functional properties that enhance shelf life and taste profile
of various food products like nutrition bars (Izzo and Niness, 2001). FOS can be used as
the sole sweetening agent and gives 34 percent calorie reduction compared with sucrose
standard. Organoleptic characteristics of the products are claimed to be very similar, with
the test sample having a lower sweetness and a softer texture. FOS can be used with
inulin to replace all the sugar and reduce the fat content and give excellent mouth feel
characteristics. Since the freezing point depression is less with oligo-fructose than with
sugar, the texture can be harder. Hard candies, gums, and marshmallows can be made
while achieving significantly reduced energy values (Murphy, 2001).
1.2.7 MODIFIED ATMOSPHERE PACKAGING
The common perception that modified atmospheres are useful for improving storability
has significant historical precedent. The written history of the use of modified
atmospheres can actually be traced back at least 2000 years to the use of underground,
sealed silos (Owen, 1800) where atmosphere modification was detected as ―foul air‖ that
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was dangerous to enter and was likely a result of O2 depletion and CO2 accumulation due
to the respiratory activity of the grain. The modified atmosphere was unintentional,
although probably beneficial. The foul air in the storages would presumably control
rodent and insect pests, thereby acting to preserve the quality and storage life of the grain.
The potential for a positive impact from alteration in the respiratory gases O2 and CO2
became increasingly known through the early research of Berard (1821), Mangin (1896),
Kidd and West (1914, 1927, 1945), and Blackman and Parija (1928).
Gas modification technologies can be segregated into two classes based on the manner in
which the atmospheres are generated and maintained. One class of technologies is
referred to as Controlled Atmosphere (CA) storage, in which the atmosphere is either
manually or mechanically controlled to achieve target headspace gas concentrations. In
CA storages, O2 and CO2 concentrations can be modulated independently from one
another. The second class of technologies is (MAP), in which a package possessing a film
or foil barrier passively limits gas exchange by the living produce enclosed in the
package, thereby altering the headspace atmosphere. In MAP, both oxygen and carbon
dioxide are modified simultaneously and their concentrations at steady state are a
function of one another. In MAP, the primary route of gas exchange may be through gas-
permeable film, perforations in film, or both. In what is referred to as active or intelligent
packaging techniques, packages may be flushed with specific gas mixtures designed to
obtain a desired initial atmospheric composition, gases may be actively released or
scavenged in the package, a partial vacuum can be imposed, biologically active materials
can be incorporated in the package, sensors may be used to respond to the product or
package conditions, and so on. The aim of MAP (passive, active, or intelligent in design)
is to take advantage of physiological responses of the enclosed plant material or plant or
human pathogens to the respiratory gases O2 and CO2. Presumably, MAP use is intended
to maintain product quality, thereby ensuring appropriate value to the consumer and
adequate cash flow back through the marketing and handling chain such that the
production and marketing system is sustainable .Knowledge of the physiological
responses to atmosphere modification is beneficial in terms of anticipating improved
quality retention as a result of technology investment (Beaudry, 2008).
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Atmosphere modification in a package requires a barrier through which gas exchange is
restricted. Enclosing an actively respiring product within a package composed all or in
part of a film that acts as a gas barrier reduces O2 and increases CO2, creating gradients
across the film barrier. These gradients provide the driving force for gas flux into or out
of the package. In passive MAP, a package always tends toward steady state, in which O2
and CO2 levels are constant and O2 uptake and CO2 production by the product are equal
to those permeating through the package, a situation that exists only when the respiratory
rate is constant or nearly so. The steady-state levels of O2 and CO2 within a package are
dependent on the interaction of respiration of the product and the permeability properties
of packaging film or micro- perforations (Beaudry et al., 1992; Cameron et al., 1989;
Jurin and Karel, 1963; Kader et al., 1989).
MAP should be carefully designed, as a system incorrectly designed may be ineffective
or even shorten the shelf life of the product. The design should take into consideration not
only steady-state conditions, but also the dynamic process, because if the product is
exposed for a long time to unsuitable gas composition before reaching the adequate
atmosphere, the package may have no benefit. The design of Modified atmosphere
package depends on a number of variables, the characteristics of the product, its mass, the
recommend atmosphere composition, the permeability of the packaging materials to
gases and its dependence on temperature and the respiration rate of the product as
affected by different gas composition and temperature. Since, respiration rate modelling
is vital to the design of MAP for fresh fruits and vegetables (Fonseca et al., 2002).
Temperature is exceptionally important in package design, continuous and perforated
films differ in their response to temperature changes. The O2 and CO2 permeability of
continuous films increases with temperature, while the diffusion of gases through
perforations is extremely insensitive to temperature changes. O2 permeation over LDPE
increases 200% in 0 to 15°C, an exchange of O2 over perforations increases only 11% at
the same temperature range. Depends on the rate of respiration and transmission, the
atmosphere modification can be achieved quickly or relatively slow. At lower
temperatures, atmosphere modification will take several days, that some package systems
cannot achieve steady-state environments prior to the end of their shelf-life. In many
21
cases, purging the package atmosphere with CO2, N2 or a combination of gases is often
desirable during filling and sealing to rapidly obtain the maximum benefits of MAP.
Product temperature affects storability more than any other factor. Pre-cooling and
temperature maintenance during handling and shipping were critical in preserving
quality. Temperature also significantly affects permeability of film and thereby the O2
and CO2 content of the package. The elevated rate of respiration at high temperature
could be used to rapidly establish the desired package atmosphere, but this would only be
useful in the few circumstances in which it would be more important to rapidly establish
the atmosphere than to slow physiological processes, eg., to reduce cut-surface browning.
Negative Responses in MAP show that respiration gets reduced as O2 becomes limiting,
but there is usually a limit to which O2 can be reduced. The lower O2 limit is frequently
considered to be the level of O2 that induces fermentation. This fermentation threshold is
not always the lower O2 limit in commercial practice, however, because lower O2 levels
may confer benefits that outweigh the loss in flavour or other quality parameters.
Ethanol, acetaldehyde, ethyl acetate and lactate are products of fermentation that can
contribute to the development of off-flavours as well as physical injury (Kays, 1997;
Mattheis and Fellman, 2000).
With regard to MAP study done by Fandos et.al (2000) on Cameros cheese, it was found
that packaging in 50%CO2/50%N2 and 40%CO2/60%N2 were the most effective
conditions for extending the shelf life of cheese with good sensory characteristics. MAP
studies have been done in iced fresh hake slices (Pastoriza et al, 1996), Fresh cut
mangoes (Aguliar et al, 2000), fresh-cut ice berg lettuce (Fan et al, 2003), refrigerated
sea bass slices (Masniyom et al, 2002), blueberry (Song et al, 2002), minimally
processed mango and pineapple fruits (Martínez-Ferrer et al, 2002), pomegranate (Artes
et al, 2000).
From the review of literature and state of the art it is clear that there are no studies on
optimization of idli with respect to components and fermentation time taking into
consideration, both instrument based texture analysis and 15mm rating scale and
combination of RSM and PCA to evolve the optimized parameters for idli. In addition
there are no studies which deal with improvement of shelf life of idli batter with modified
22
atmosphere packaging. In continuation with this, the present study has been planned with
an objective to improve the shelf life of ready to cook idli batter using modified
atmosphere packaging.
The set objective is achieved through following the three major sub-objectives:
1. To understand the presently followed practices for the preparation of idli.
2. To optimize the process of preparation of the product with respect to
ingredient ratios and fermentation time.
3. To improve the shelf-life of ready to cook idli batter by optimized process.